Enough water, but not too much, is delicate balance

by Diana Balazs - Jun. 9, 2007 12:00 AMSpecial for the Republic

Question: I live in Queen Creek. Four weeks ago, a local nursery planted two 24-inch box trees - a sissoo and a Shamel ash - in my backyard. Both seem to be doing poorly, mainly, I suspect, from improper watering; most of the leaves of the sissoo are yellow. The Shamel's leaves are curling or wilting, a few are dead, some becoming brown-spotted, and overall appearing shriveled and wilted.

Both trees are exposed to full sunlight, and are being watered daily for one hour, each tree receiving 10 gallons of water. At the end of the one-hour watering time, both trees have about 2 inches of water standing in their wells. The sissoo drains in about an hour, the Shamel ash takes two to three hours.

I've talked to two different (nursery) people and have gotten two different answers: too much water and not enough water. In any case, they remind me that I have a 90-day guarantee on the trees. (Big deal, if they happen to die six months or a year from now.) At my wit's end, what with nursery "experts' " advice, which seems to be more of a guessing game than anything resembling helpful knowledge.

- David Romero, Queen Creek

Answer: Your two trees are letting you know they are stressed. If your soil is good and the roots have not been damaged, then I suspect your daily watering is doing more harm than good. Your trees' roots need to establish themselves.

If you apply too little water, your roots will be stressed, seek out surface water and grow shallow. If you water too much, they literally will drown because they can't take in needed oxygen.

For newly planted trees, you should water so that the moisture penetrates to a depth of about 3 feet. Take a long stick (a broom handle will do) and push it down into each tree well after the water has drained to see how deep the moisture has traveled.

How often you water also is important. Desert Botanical Garden in Phoenix suggests this first-year watering guide for newly planted trees:

- If the temperature is more than 108 degrees - water every two to three days.

- 101-108 degrees - once a week.

- 90-100 degrees - every 10 days.

- 75-89 degrees - every two weeks.

- Below 75 degrees - every three weeks.

- If you are using a drip irrigation system, be sure that the system runs at least two hours for each watering. This will ensure that the plant is being watered deeply. About every fifth watering, let the drip run for 8-10 hours. This will leach away salts.

Good luck. If your trees don't perk up in the next month, take your nursery up on its guarantee.

Virtual garden:If you've got fountain grass growing in your yard, you might reconsider, the Arizona Native Plant Society advises. Go to aznps.org and click on "invasives" to learn why fountain grass, buffelgrass and other invasive plants do more harm than good in the desert.

A greener thumb: Here is a tip from Desert Botanical Garden about soil types and watering needs:

Soils with a high clay content hold moisture well, too well for some desert plants, and could be amended with a small amount of organic matter and coarse sand.

Send garden-related questions, Web site suggestions and tips to Southwest Gardens, in care of Diana Balazs, The Arizona Republic Scottsdale Bureau, 8800 E. Raintree Drive, Suite 250, Scottsdale, AZ 85260; via e-mail to diana.balazs@arizonarepublic.com; or via fax to (602) 444-6875. Include your full name and the city you live in and a telephone number. Your number will not be published.